“We’ve been talking about climate change in Washington for years and energy independence and efficiency for years,” Obama said. “But no matter how many scientists testified about greenhouse gases, no matter how much evidence that they’re threatening our coasts and endangering our weather patterns, nothing happened with global warming until now.”

The Illinois senator stood in front of University of New Hampshire campus buses that run on biofuels.

Obama says the fuel used to power automobiles should contain less of the carbon that contributes to global warming — enough to make the same impact as taking 32 million cars off the road.

“I believe we still have a chance to pass on a planet to our children that is cleaner and safer and more prosperous than we found it,” Obama said. “This is our generation’s moment to save future generations from global catastrophe.”

Obama’s approach echoes California’s. The state’s Republican governor, Arnold Schwarzenegger, issued an executive order this year requiring all fuels sold in the state to contain less carbon. The goal is to reduce carbon dioxide emissions from passenger vehicles 10 percent by 2020.

The Obama campaign said its effort would take that plan nationally. Specifically, Obama wants to cut greenhouse gas emissions from cars by 5 percent in 2015 and 10 percent in 2020.

“It will take a grass-roots effort to make America greener and end the tyranny of oil,” Obama said two days before Earth Day.

Obama’s plan counts on new limits to stimulate increased production of renewable biofuels, such as corn and cellulosic ethanol, which naturally have lower emissions. The plan would create incentives for increased research, investment in cleaner fuels and flexible-fuel vehicles that can run on ethanol.

The campaign says a national fuel standard would reduce greenhouse gas emissions by about 200 million tons in 2020, compared with 2007 levels — the equivalent of taking about 32 million cars off the road in 2020. The campaign also estimates the annual consumption of gasoline derived from foreign oil imports would drop by about 30 billion gallons in 2020.

Obama also has proposed a bill in the Senate that would raise fuel efficiency standards. If that were enacted and combined with his carbon program, it would cut about 583 million tons of greenhouse gases in 2020, the equivalent of taking about 96 million cars off the road.

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